Induction coil



Nov. 16,1926. Leoas F. E. FIELD INDUCTION COIL Filed April 8. 1922l PaienieaNoia-iezsp 'i l y 1,606,7'1V55l.

UNITED- STATES.N PATENT OFFICE. 1

FRANK FIELD, v0F SOMERVILLE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N.' Y.,` CORPORATION 0F NEW YORK.

INDUCTION COIL.

.Application led April 8, 1922. Serial No. 550,806.

This invention relates to induction coils have a low inductance; Fig. 2 illustrates the and its object is to provide a convenient and saine number of pieces of magnetic material simple methodof adjusting the inductance arran ed in such a mannerV as to give the of van induction coil.V trans ormer winding a high inductance; Fig.

'Commercial transformer windingsA with 3 represents the pieces of the core arranged n equalnumber ofturns and mountedon the in a manner to give the transformer winding same size core do not always have the same an inductance intermediatethe values resultvalue of inductance. This variation, which ing from the arrangements of'Figs. 1 and 2; may be as muchas 30 per cent or more, is and Fig. 4represents a signaling circuit emsometimes of no special concern, but it may ploying a transformer constructed in acu be a disadvantage in cases where it is desired cordance with this invention. that awinding shouldhave a definite pre- Referring in detail to the drawings, Fig. determined value ofinductance, for example, 1 discloses atransformer having a core of when it is'desired to sharply resonate one of magnetic materialy composed of a lurality the transformer windings with a fixed ca- .of F-sha'ped pieces. 10 and a plurality of L- 70 pacity at4 one particular frequency. Shaped pieces 11 held in position `by two The invention is hereinafter described in clamping plates 12 and 13 and by a pluconnection with-a transformer having a subrality of bolts 14, 15, 16, and 17.V Mounted stantially closed magnetic circuit core comon the portion 18 of the F-shaped pieces, is posed of a plurality of laminations.v Each a spool comprising a primary winding 19 15 laminationconsists of a plurality of separate and a secondary winding 20. Leads 21 and pieces of core material, the points where the 22 may represent the terminals of the pripieces of each layer come in contact with mary Wlndlng Whlle leads 23 3nd 24 the each other forming small air gaps -for the terminals of the secondary winding.l l purpose ofreducing the variation with re- It has been found that Whenthe F and 30 quency of thepermeability of the core. The L- Sllapd PleCeS are arranged as in Fig. 1 pieces forming each layer may, for example, with all 'the L-shaped pieces on one side be F-shaped' and L shaped, which, when and all the F-shaped pleCeS 0n.I the other placedtogether, form a two-mesh magnetic Side, that the .llldUCtaIlCe 0f the primary core.; i winding 19 is relatively low. However, if 35 In accordance with this invention, it has the F H Ild Lf-Shaped Pefes alf@ Stgflffl 0H@ fr been found that the transformer winding at a tlmes 21S ShOjifn 111 Flg. 2, eac-iiv side. will have the maximum inductance when the 0f the C0re C0mP1`1S1ng nqual Dumber 0f F and L-shaped piecesV are staggered one at L-shaped pieces, then the inductance of the a time, and thatvtvhe inductance will be of Dlflmaly. wlndlng 19'vv1ll be considerably I0 minimum value when al1 the L Shaped pieces higher than obtained with the core arrangeare on one side of the core and all the F- ment 0f F195- 1a @mi may be 3S much @5 30 shaped pieces are on the Aother side, while ,01' 40 Per Cent hlgheli-O? m91@ dependmg Staggeringthem 2, 3` 4 0r more at a time, upon the number of laminations employed. will giveavalue interni and minimum` values. The method of this and L-Shapedpeces 23, 4e 0l' THON? at a invention, therefore, comprisesl placing the' 11,1163 *that the lndllctan 0f the Pma'y winding on the corewith the laminations or Wlmllg, When measurd Under the Sam@ i pieces of the core arranged in a suitable man- @O ndtlons 3S employed m th@ measurement ner. measuring the inductance of the winding 21th the arrangements 0f FlgS- and 2, l and' the-n staggeringa plurality of the strips hfES a Vahle ntemedlte the mxlmllm and in such a. manner as to produce the necesmlmmum Yilues 'Obtamed by these arrange' sary change in the inductance to give the dements. Fig. 3- for example, shows the F Sird result, and L-shaped pieces staggered several at a For` a better understanding of the invent1m@- tion, reference is made to the accompanying ,When the laminations are arranged as drawings in which Fig. 1 represents a trans- Shown 1n Fig. l, a complete air-gap is former with the pieces 'of magnetic material ormed'in the magnetic circuit and the reforming the core arranged'in such a manner luctance of the magnetic path is relatively as to cause one ofthetransformer- Windingsto high, giving the primary Winding a relal ediate the maximum 'It has also been found that staggering the l tively low inductance. On the nther liand,l

when the aps are sta gered as shown'in tions being negligible. .The 'reluctance of f such avcircuit is therefore low, resultxngm if f a hi h inductance of the rimarywindings. i

fIn t e arrangement of t e ga s shdwn'ln Fig. 3, in order to form a comp ete--iron'cilcuit, the flux must pass through several airaps between the faces of the ad'oining iminations. While the reluctance' o a. single gap between the. faces of the laminations is negligible, the reluctance of a -series of such ga s must be considered. The reluctance o the magnetic path is thereforeY somewhere between that of Figs. 1 and 2 and results in an intermediate inducta'nce of the primary Winding. Therefore p proper groupin of the gaps, the inductance may be varie between the limits represented by Figs. 1 and 2.

The method winding in accordance with 'y this invention,

is, therefore,jto place` the winding ona'core which has the'l laminations arranged in",v any suitable manner,'measuring the lnductance of the winding and .thereby ascertaining how much the actualnductance of the winding varies from the desiredjvaluefand thenrefv arranglngy the laminatlons'of the ,core'1n,

such a manner that the airgapsdn Ia'jplu.

rality of laminations occur 'atdifferentl is found that the inductance ofthe. windin on the core is too low, the Fv and L-shap 2, or 1 at a time, dependin on how pieces may be staggered 6, 7, 8 or morel at a time, o'r. may-be-l arranged as shownin .si e of the-coi-'eand all `of the L-shaped pieces on the other iside, depending on how. great a changeof inductance is desired. i This method afpvarying the inductance` of particular; vimp'or'ftance.when it is incon-` .fvenient or impossible tovary the inductance ofa .winding by increasing jordecreasing f fthef number'.v of turns thereof. [For example,

ginfthei-transformer sln'iwn in'jFig'. 1, Windl ing* '1th'isaunderneathv the@'secondaryaWind- A f ingV 20and. it would-,therefore behighly objectionabl'e"to' unwind the secondary., wind- Ving 2Ozingoxjder toA lchange thenumber of by the .rily bei.: manufactured wi l y i;` the `same value4v ofA inductancel or their pr1- lomts 1n the core than ,they` di'dywith 'the st arrangement. For example, .if the core is made up, as shown in. Fig,v anditf `fits core 38. "1 -1"'..Whileg .,this, abovein'connection with the construction of Lacona the transformer and .thef laminationsfof the or'e rearranged in anysuitable manner withlout danger opifdamaging the transformer Fight transformer, constructedinjjaccordance with this invention, may, be vused @tol-' advantage ina s1 ahng system. @BOfis-a vacuum tube am lifier of e three-electrode type arrange inthe usual manner for repeating signals between the-associatedfgline sections 31 and 3 2. lIn someinstancesv it maybe desirable `to selectively .amplify and impressmonfline sectionuZ- o'n'e yparticular frequency *or a narrow-.band of frequencies present in line'section-31;?q0ne arrangement for doing this is to connect acondenser 34 in shunt to the v.f1-primary vwindingl 35v ofthe input transf varying' the yeffective 'inn ductance of a retard coil or va transformen ormer 36: of the re eater.'-The values of the capacity 34 `and t e inductance of winding 3 5 should be suchthat they form a circuit fantifresonant tothe fr uency desired to be selectively" amplified. "Since it is much 4cheaer and more convenient to f'emlploy a fixe {condenser instead of yavariab e condenser in shunt 'to thev rimary windinit 1n followsthat input trans o rmers employe connections such -as lshould necessatii a proximatelr ma v windingsfrso' .that whenf, the l.primary win ing of. each,A transformer is connected in." c ircuit'fwith .thejfxed condenser, the two "'elements will beanti-resonant at vthe .de sired freq'uencyg.-A As pointed out above, 'the pieces, instead lof being staggered lfoury ati a time, for example, may be staggered 3, greatV an increase4 in inductance 1s desired. If, l on the other hand, the inductance vof the` winding as measured with the arrangement.' cf Fig. 3,' is too high, the Fand L`shaped .inductanceofprimarygiwindin `35 maybe Aadjusted' togthe'desiredyaluej y a suitable .arrangement of` thef,laininations lcomprising a transformer-"employin v, La'jtWo-mesh core ofmagnetic "material, ji't V51s 'to be understood that the-methodsi'oithis"invention are ap- F1 1, w1th'allthe F-shaped pleceson one" plicable to transformers of. one mesh or -severalsmeshespand:although the core described'.rv :inv ,f detail,l' haail been illustrated as compose'dfbf'- F-'shaediand L-shaped pieces, itis obviousfthatft is` invention can be employedjwith transformer laminations of othershapes,- l

- l In the: art'gfmanufacturing inductances employinglj'cores"builtzilp from laminatons tion, the method of adjusting the inductance serting them in reversed order to vary the of each unit to a required value comprising number of contiguous layers with coincid- 10 assembling the coil and the core -using ing air-gaps, and continuing the measuring groups of laminations with thel air-gaps in and rearranging procedure until the units the layers coinciding within each group and have the required inductance values. alternating from group to group, measur- In witness whereof, I hereunto subscribe ing the inductance of the assembled coil, my name this 3rd day ofAprill A. D. 1922.- v withdrawing lamination sections and rein- FRANK E. FIELD. 

